John Gill Commentary 1 Chronicles 12:39

"And they were there with David three days, eating and drinking; for their brethren had made preparation for them." — 1 Chronicles 12:39 (ASV)

And there they were with David three days, eating and
drinking
Keeping a festival, to testify their joy on this occasion:

for their brethren had prepared for them
not the inhabitants of Hebron only, but all the country round about, brought in provisions on this joyful occasion; otherwise the men of Hebron would not have been able to have provided what was sufficient for such a vast number, as appears by what follows.